Removal of flexible sheets from rotary drums

ABSTRACT

A flexible sheet clamped at one end to a rotary drum to permit rotation of the drum with the sheet entrained therearound is unloaded from the drum by reversing drum rotation and providing a separating member which comes between the drum surface and an opposite end portion of the sheet and progressively lifts the sheet from that surface as reverse drum rotation continues, the means clamping the sheet to the drum being released before the clamped sheet end reaches the separating member.

1 United States Patent V [191 1111 3,839,958 Kent et al. Oct. 8, 1974 [54] REMOVAL OF FLEXIBLE SHEETS FROM 2,821,950 2/1952 Mazlzio et =11. l0l/l32.5 ROTARY DRUMS 3,062,l 5 ll I96 Tay or et a 101/132 X 3,181,459 5/1965 Ritzerfeld et al. 101/1325 [75] Inventors: Alan Walter Kent, Frimley; Kenneth Walter ORiley, Weybridge, both of England Przmary Exammer-Stephen C. Pellegrmo V. W ,Y .1 new, Attome ,A ent, or Firm-Thomas C. Wettach; [73] Assignee: Viekers Limited, London, England p si [22] Filed: Oct. 9, 1973 30 F A D A flexible sheet clamped at oneencl to a rotary drum 1 O t 2 g gq ata 505/72 to permit rotation of the drum with the sheet en- 6 feat am trained therearound is unloaded from the drum by reversing drum rotation and providing a separating ifiif member which comes between the drum surface and 58] d 132 132 5 an opposite end portion of the sheet and progressively 0 are 1O1/9'1f29/426 lifts the sheet from that surface as reverse drum rotation continues, the means clamping the sheet to the drum being released before the clamped sheet end [5 6] U E S g :;ENTs reaches the separating member.

2,758,539 8/1956 Ritzerfeld et al. l0l/l32 X 13 Claims, 5 Drawing Figures PATENTEDDET 81974 sum 2 or 3 FIG. 4.

PATENTEU OBI 81974 SHEET 3 BF 3 REMOVAL OF FLEXIBLE SHEETS FROM ROTARY DRUMS This invention relates to the unloading of flexible sheets from rotary drums and is applicable, for example, to the unloading of a stencil from a duplicator drum.

With rotary apparatus of the kind comprising a rotatably mounted drum provided with sheet clamping means for releasably clamping one end of a flexible sheet to the drum while the drum is rotated by drive means of the apparatus, it has hitherto been common, for example in the case of rotary duplicating machines, to remove the sheet from the drum manually after use. It is an object of the present invention to provide means whereby such sheet removal can be effected in simple manner without the need for manual operation.

According to the present invention, there is provided rotary apparatus of the kind comprising a rotatably mounted drum having a circumferential surface and provided with sheet-clamping means for clamping at a predetermined location on the circumferential surface a leading edge portion of a flexible sheet whichextends around that surface, from said leading edge portion, in a given direction; said apparatus including:

reversible drive means coupled to' said drum and changeable between a forward-drive condition, rotating said drum in the direction opposite to said given direction, and in a reverse-drive unloading condition rotating said drum in said given direction;

a separating member for removing the sheet from said circumferential surface;

a positioning mechanism supporting said separating member, movable between a non-operative disposition, for holding the separating member away from said drum, and an operative position for interposing said separating member between said circumferential surface and said sheet when said drum means are in said unloading condition; and I clamp-release means, defining a sheet-end release position for the drum, arranged to de-actuate said sheet-clamping means whensaid drive means rotating the drum in said given direction bring the drum into said sheet-end release'position. I

The invention is applicable to the unloading of a flexible stencil sheet from the duplicator drum of a rotary duplicating machine such as disclosed in British Patent Application No. 57786/72. In such a duplicating machine, the duplicator drum is provided with sheet clamping means adapted to grip a leading edge portion of the stencil sheet so that as the duplicator drum rorates the rest of the stencil sheet is entrained around the surface of the drum. By reversing the direction of rotation of the drum and positioning a separating member adjacent thereto the stencil sheet will be progressively lifted from the surface of the drum over the separating member as the drum continuesto rotate in the reverse direction. If the sheet clamping means are operated so as to release the gripped edge portion of the stencil sheet before that edge portion reaches the separating member, the sheet will be drawn off the drum cornpletely. Generally, most of the drum surface will be inked for the purpose of reproducing the stencil wound around the drum. Because of the tackiness of the ink employed at the drum surface, any tendency for the inertia of the trailing edge portion of the stencil sheet to the drum surface is prevented during duplicating. So that the trailing edge portion of the stencil sheet does not itself become attached to the drum surface, a noninked, preferably metal portion of the drum surface is provided in the vicinity of the trailing edge portion of the stencil sheet. In this way subsequent separation of the stencil sheet from the drum surface upon rotating the drum in reverse is not impeded.

Rotary apparatus embodying the invention may also take the form of a rotary printing machine. In this case one end of a flexible sheet form printing plate is clamped by the sheet clamping means so that as the rotary drum of the apparatus is rotated the rest of the plate is entrained around the circumferential "surface of the drum and, in combination therewith, serves as a printing cylinder in the machine. The plate may for example be an electrostatic or other paper-master for lithographic reproduction.

The separating member employed in apparatus embodying the invention can take various forms. Where the separation of a stencil sheet from a tacky inked surcause lifting of the remainder of the stencil sheet from face is concerned, however, the area of the separating member coming in contact with the inky undersurface of the 'stencilsheet should be kept me minimum since otherwise the sheet may adhere to the separating member so strongly during separation that the portion of the, sheet between the drum and the separating member may buckle or that the sheet may be unable to fall away from the separating member under the action of gravity following release of the sheet from the claniping fneans.

Accordingly, the separating member preferably comprises an elongate member arranged'to extend substatitially parallel to the axis of rotation of the drum. Ad-

vantageously, this elongate member is a length of filamentary material, for example a metal or plastics filament, which, at least when brought up adjacent to the drum surface, extends more or less parallel to the druiii axis. Alternatively, the elongate member may be a length of tape, preferably narrow tape, ora knife-edged member. Where a tape or filament. is involved,- it should be suitably tensioned to carry out; its function.

In the application of the invention to the separation of flexible electrostatic or other papermasters in a rotary lithographic printing machine, more substantial separating members with greater areas of contact can be employed since, in this case, tackiness due to ink is not generally a problem. t V i The separating member employed in an apparatus embodying the invention is preferably supported by the positioning mechanism for pivotal movement about an axis substantially parallel to the axis of rotation of the rotary drum.

When unloading a flexible sheet from a rotary drum in accordance with the present invention, the exact timing of the commencement of reverse rotation of the drum relative to the bringing of the separating member into its operative position adjacent to the drum is not critical. The separating member should however be in position by the time that the trailing edge of the sheet reaches the separating location in the course of the reverse rotation of the drum.

For automatic control of sheet release, there may be provided clamp-release means arranged to bring about release of the previously clamped end of a flexible sheet by the clamping means when, in the course of reverse rotation, the drum reaches the predetermined sheet-end release position. The clamp-release means may for example be provided with a solenoid for controlling operation of the clamp-release means. In this case the clamp-release means may for example include a clamp control cam with which the solenoid is coupled to control the cam so that when brought by the action of the solenoid from a non-operational position into an operational position in the path of rotation of a cam follower which is mounted, movably relative to the drum, for rotation in synchrony with the drum and is controllingly coupled with the sheet clamping means, the cam moves the cam follower into a clamp-release disposition when, in the course of reverse rotation, the drum reaches the predetermined sheet-end release position.

The positioning mechanism arranged to bring the separating member into its operative position adjacent the drum so as to come between the circumferential surface thereof and the free end portion of a clamped sheet when the drum is rotated in reverse may be provided with a solenoid arranged to control movement of the positioning mechanism between its operative and non-operative dispositions. Switch means may be provided to control energization of either solenoid in dependence upon the rotary position of the drum. 7

For a better understanding of the invention, and to show how it can be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:

FIGS. 1, 2 and 3 are respective like schematic sectional views of rotary duplicating apparatus embodying FIG. 4 is an end view of part of the apparatus, and

FIG. is a fragmented perspective view of part of the apparatus.

The illustrated apparatus comprises a duplicator drum 1 arranged so that it can be rotated about its rotary axis both in a particular direction for the purposes of duplicating,-and in reverse. The drum 1 is provided with stencilsheet clamping means comprising a fixed clamping jaw 2, which extends axially of the drum at a circumferential location thereon, and a cooperating movable clamping jaw 3 which also extends'axially of the drum. The movable clamping jaw 3 is movable from a first position, for which the sheet clamping means are in an open condition allowing an end portion of a sheet to be inserted between the clamping jaws 2 and 3, and a second position for which the clamping means are in a closed condition in which the clamping jaws 2 and 3 will grip between them any such end portion inserted therebetween while the clamping means were in the open condition.

One end portion of a stencil sheet 4 is shown in FIG. 1 gripped between the closed clamping jaws 2 and 3 while the rest of the sheet extends around the external surface of the drum. Most of the'stencil sheet extends adjacent to an inked surface portion 5 of the drum to which the sheet thus adheres on account of the tackiness of the ink. The sheet 4 has a trailing edge portion 6, however, which is adjacent to a non-inked metal circumferential surface portion 7 of the drum 1. During duplicating, the drum 1 rotates in the opposite direction to that indicated by the arrow A. For the purposes of unloading the stencil sheet 4 from the drum 1, however, the drum is rotated in the direction of the arrow and a pair of parallel arms 8 (only one visible in FIGS. 1 to 3 and neither visible in FIG. 4) supporting a metal the invention at three stages in the operation thereof,

or plastics filament 9 extending parallel to the axis of the drum 1 is pivoted, from the position indicated in FIG. 1 remote from the drum, to the position indicated in FIG. 2 adjacent to the drum. The filament 9 thus comes between the end portion 6 of the sheet 4 and the adjacent surface portion of the drum 1 as the drum is rotated in the arrowed direction. Consequently, the remaining part 10 of the sheet 4 is progressively lifted from the surface of the drum 1 as the drum rotates, as shown in FIG. 2.

Prior to arrival of the clamping jaws 2 and 3 at the separating location as the drum 1 continues to rotate, the sheet clamping means are opened. This allows the previously gripped end portion of the sheet 4 to fall away from between the clamping jaws 2 and 3 so that the sheet can be completely separated from the drum.

As will be described hereinafter in greater detail with reference to FIG. 4, the operation of the clamping jaw 3 is controlled with the aid of a clamp control solenoid S, which when energized causes a clamp control cam 11 pivotable about an axis fixed to the apparatus (see FIG. 4) to be brought into an operational position in the path of rotation of a cam follower 12 which rotates in synchrony with the duplicator drum 1, this cam follower serving to control the clamping means. When the clamp controlcam 11 is in its operational position the cam follower 12 is cammed for part of each rotation of the drum so as to cause the clamping jaw 3 to be held apart from the clamping jaw' 2 for that part of the rotation.

Rotation of the drum is controlled with the aid of a microswitch 13 which is arranged to cooperate with a cam 14 that rotates in synchrony with the drum 1. When cammed, the microswitch 13 is in an open condition in which, normally, drum rotation is prevented. Since, when the apparatus is in the ready-for-unloading condition illustrated in FIG. 1, the microswitch 13 is cammed open by the cam 14, to start rotation of the drum 1 the microswitch 13 must be overriden by a start button (not shown).

Bringing-up of the separating filament 9 supported between the arms 8 is controlledwith the aidof a microswitch 15 arranged to cooperate with a cam 16 which, like the cam-l2, also rotates in synchrony with the drum 1. When cammed by the cam .16 from a normally open condition into a closed 'condition, the microswitch 15 brings about energization of a solenoid S which, when energized, causes the separating filament 9 to be moved to and held at the separating location adjacent to the surface. of the drum 1 for the duration of the energization. Camming of the microswitch 15 into its open condition by the cam 16 is also arranged to bring aboutenergization of the clamp control solenoid S,, so that while the microswitch 15 remains cammed in its closed condition the clamp control cam llis held in the path of rotation of the cam follower 12 for operating the clamping means.

The illustrated apparatus operates as follows: Initially the apparatus is in the ready-for-unloading condition illustrated in FIG. 1, in which the microswitch 13 is held open by the cam 14, thereby preventing rotation of the drum 1. To start rotation, the abovementioned start button is pressed, thereby overriding the microswitch 13. With the pressing of the start button the drum 1 begins to rotate in the direction of the arrow A. After the drum has rotated through a small angle, say 3 or so, the cam 14 has rotated sufficiently to allow the miroswitch 13 to return to its closed condition; once the microswitch 13 is in its closed condition, rotation of the drum will thus continue whether or not the start button remains depressed.

After the drum 1 has rotated a little further, say about 6 or so, the microswitch is cammed by the cam 16 into its closed condition, thereby energizing the clamp control solenoid S and the solenoid S controlling the position of the separating filament 9. Accordingly, the clamp control cam 11 is brought into its operational position in the path of rotation of the cam follower 12 for controlling the clamping means, and the supporting arms 8 are pivoted to a position in which the separating filament 9 is at the separating location adjacent to the drum surface.

As the rotation of the drum in the direction of the arrow A continues, the end portion 6 of the stencil sheet 4 passes over the separating filament 9 on that side thereof remote from the drum surface. Consequently, as described above and as illustrated in FIG. 2, the rest of the stencil sheet 4 is progressively lifted from the surface of the drum as the rotation continues, the already-separated length of the sheet falling away from the location of the separating filament 9 under gravity.

7 By the time that most of the stencil sheet 4 has been separated in this manner from the surface of the drum 1, the drum has rotated sufficiently, say 220, for the clamp-control cam follower 12 to have reached the location of theclamp control cam 11. Accordingly at this point in the rotation of the drum, the clamping jaw 3 is moved away from the clamping jaw 2 so as to release the previously clamped end portion of the stencil 4. Thus, with continuing rotation of the drum 1, the stencil 4 can be completely separated therefrom by the separating filament 9 at the separating location. FIG. 3 illustrates the apparatus when the clamping means have been opened to allow release of the previously gripped edge portion of the sheet 4. j

' Iii the time that the sheet 4 beensepatatarisfii the drum surface, the drum has rotated sufficiently for the cam 16 to have rotated sufficiently for the microswitch 15 to be no longer held cammed in its closed condition by the cam. Accordingly, the solenoids S and S are de-energized and hence the arms 8 are pivoted back to a position in which the separating filament 9 supported between them is away from the separating location and, simultaneously, the clamp control cam 11 returns to an inoperative position, thus permitting closure of the clamping means. Upon performing a com plete revolution, the cam 14 is once more brought into a position in which the cam 14 cams the microswitch 13 into an open condition and rotation of the drum thus stops, the apparatus being in the same condition as illustrated in FIG. 1 except that the sheet 4 has now been removed from the surface of the drum.

The control of drum rotation by the microswitch 13 may be effected by employing the microswitch to control an electromagnetic clutch (not shown) between drum gearing and drive means for the drum.

Clamp-release means for effecting release of the sheet clamping means are illustrated in FIG. 4. From FIG. 4, it can be seen that the position of the clamping jaw 3, which is mounted on the drum 1 so as to be pivotable about an axis parallel to the rotary axis of the drum, is controlled by an abutting cam actuating lever 17 also mounted on the drum so as to be pivotable about an axis parallel to the rotary axis of the drum. At an end portion thereof remote from the clamping jaw 3 the above-mentioned cam folllower 12 is pivotally mounted on the clamp actuating lever 17. The cam 11 with which the cam follower 12 is adapted to cooperate is supported on a cam support arm 18 which is pivotally mounted about an axis parallel to the axis of the drum but fast with respect to the apparatus as a whole. The position of the cam 11 is controlled by a cam actuating lever 19 which is pivotally connected at one end thereof to the cam 11. The other end of the cam actuating lever 19 is pivotally connected to a sole noid arm 20 whose position is controlled in dependence upon energization of the solenoid 8,. When the solenoid S is energized, the solenoid arm 20 is moved from the position thereof indicated in dashed lines to the position thereof shown in full lines. Accordingly, the-cam l is moved from a non-operational position away from the path of rotation of the cam follower 12 into an operational position in that path of rotation. Thus while the solenoid 8, remains energized, the cam follower 12 will be cammed for part of every revolution of the drum into a clamp-release disposition in which the clamp actuating lever l7 is caused to hold the clamping jaw 3 apart from the clamping jaw 2 fixed relative to the drum. While the solenoid S is unenergized,

however, the cam 11 will be out of the path of rotation of the cam follower 12 with the drum 1, and so the clamping means will remain in the closed condition (as shown in dashed lines).

The positioning mechanism for bringing the separating filament 9 into its operative position adjacent to the surface of the drum 1 is illustrated in FIG. 5. As can be seen from this figure, the parallel arms 8 between which the separating filament 9 is supported in tension extend from a common support shaft 21 which is aligned along an axis parallel to the axis of rotation of the drum 1. An actuating arm 22 extending from the support shaft 21 is coupled to the solenoid S sothat, when energized, the solenoid pulls the actuating arm downwards as seen in FIG. 5, thereby causing the support shaft 21 to be rotated about its longitudinal axis by a certain amount. This in turn causes the arms 8, and thus the separating filament 9, to be swung from the illustrated disposition thereof to the disposition indicated in dashed line, which latter disposition corresponds to the operative position of the separating filament 9. On subsequent de-energization of the solenoid S the separating member 9 resumes its inoperative position.

While the invention has been described with reference to a duplicating apparatus, it will be appreciated that the invention could be employed in other fields, for example in separating flexible electrostatic masters from drums in offset litho machines, where it is already the practice to leave an unclampedl end portion of the master trailing free during rotation. Further, it will be understood that the sheet clamping means of apparatus embodying the invention, and any clamping or rotation control means thereof, may take forms different from those described with reference to the drawings. The sheet clamping means might for example comprise two co-operating clamp members each of which is movable relative to the drum.

tends around that surface, from said leading edge portion, in a given direction; said-apparatus including:

reversible drive means coupled to said drum and changeable between a forward-drive condition, rotating said drum in the direction opposite to said given direction, and in a reverse-drive unloading condition rotating said drum in said given direction; separating member for removing the sheet from said circumferential surface; positioning mechanism supporting said separating member, movable between a non-operative disposition, for holding the separating member away from said drum, and an operative position for interposing said separating member between said circumferential surface and said sheet when said drum means are in said unloading condition; and clamp-release means, defining a sheet-end release position for the drum, arranged to de-actuate said sheet-clamping means when said drive means rotating the drum in said given direction bring the drum into said sheet-end release position.

2. Apparatus as claimed in claim 1, wherein said separating member comprises an elongate member held extending substantially parallel to the axis of rotation of said drum.

3. Apparatus as claimed in claim l, wherein said separating member is a length of filamentary material.

4. Apparatus as claimed iniaiiiii, wherein said separating member is a length of tape.

5. Apparatus as claimed in claim 1, wherein said separating member is a knife-edged member.

6. Apparatus as claimed in claim 1, wherein said separating member is supported by said positioning mechanism for pivotal movement about an axis substantially parallel to the axis of rotation of said drum.

7. Apparatus as claimed in claim 1, wherein said clamp-release means are provided with a solenoid ar- 8 ranged to control operation of said clamp-release means.

'8. Apparatus as claimed in claim 7, wherein said .clamp-release means include:

a clamp control cam movable between an operational position and a non-operational position, said solenoid being controllingly coupled with said cam for bringing about movement of said cam between said operational and non-operational positions; and

cam follower mounted, movably relative to said drum, for rotation in synchrony with said drum along a given path of rotation in which said operational position is located, said cam follower being controllingly coupled with said sheet-clamping means for de-actuating said sheetclamping means when said cam follower is moved into a clamprelease disposition; said cam co-operating with said cam follower, when with said cam in said operational position said drum is rotated in said given direction into said sheet-end release position, to cam said cam follower into'said clamp-release disposition.

' 9. Apparatus as claimed in claim 1, wherein said positioning mechanism is provided with a solenoid arranged to control movement of said positioning mechanism between said operative and non-operative dispositions.

10. Apparatus as claimed in claim 8, including switch means arranged for controlling energization of said solenoid in dependence upon'the rotary position of said drum.

11. Apparatus as claimed in claim 9, including switch means arranged for controlling energization of said solenoid in dependence upon the rotary position of said drum.

12.Apparatus as claimed in claim 1, said apparatus constituting a rotary duplicating machine in which said drum is a duplicator drum for supporting a stencil sheet. A

13. Apparatus as claimed in claim 1, said apparatus constituting a rotary printing machine in which said drum is a support drum for supporting a flexible sheetform printing plate. 

1. Rotary apparatus of the kind comprising a rotatably mounted drum having a circumferential surface and provided with sheetclamping means for clamping at a predetermined location on the circumferential surface a leading edge portion of a flexible sheet which extends around that surface, from said leading edge portion, in a given direction; said apparatus including: reversible drive means coupled to said drum and changeable between a forward-drive condition, rotating said drum in the direction opposite to said given direction, and in a reversedrive unloading condition rotating said drum in said given direction; a separating member for removing the sheet from said circumferential surface; a positioning mechanism supporting said separating member, movable between a non-operative disposition, for holding the separating member away from said drum, and an operative position for interposing said separating member between said circumferential surface and said sheet when said drum means are in said unloading condition; and clamp-release means, defining a sheet-end release position for the drum, arranged to de-actuate said sheet-clamping means when said drive means rotating the drum in said given direction bring the drum into said sheet-end release position.
 2. Apparatus as claimed in claim 1, wherein said separating member comprises an elongate member held extending substantially parallel to the axis of rotation of said drum.
 3. Apparatus as claimed in claim 1, wherein said separating member is a length of filamentary material.
 4. Apparatus as claimed in claim 1, wherein said separating member is a length of tape.
 5. Apparatus as claimed in claim 1, wherein said separating member is a knife-edged member.
 6. Apparatus as claimed in claim 1, wherein said separating member is supported by said positioning mechanism for pivotal movement about an axis substantially parallel to the axis of rotation of said drum.
 7. Apparatus as claimed in claim 1, wherein said clamp-release means are provided with a solenoid arranged to control operation of said clamp-release means.
 8. Apparatus as claimed in claim 7, wherein said clamp-release means include: a clamp control caM movable between an operational position and a non-operational position, said solenoid being controllingly coupled with said cam for bringing about movement of said cam between said operational and non-operational positions; and a cam follower mounted, movably relative to said drum, for rotation in synchrony with said drum along a given path of rotation in which said operational position is located, said cam follower being controllingly coupled with said sheet-clamping means for de-actuating said sheet-clamping means when said cam follower is moved into a clamp-release disposition; said cam co-operating with said cam follower, when with said cam in said operational position said drum is rotated in said given direction into said sheet-end release position, to cam said cam follower into said clamp-release disposition.
 9. Apparatus as claimed in claim 1, wherein said positioning mechanism is provided with a solenoid arranged to control movement of said positioning mechanism between said operative and non-operative dispositions.
 10. Apparatus as claimed in claim 8, including switch means arranged for controlling energization of said solenoid in dependence upon the rotary position of said drum.
 11. Apparatus as claimed in claim 9, including switch means arranged for controlling energization of said solenoid in dependence upon the rotary position of said drum.
 12. Apparatus as claimed in claim 1, said apparatus constituting a rotary duplicating machine in which said drum is a duplicator drum for supporting a stencil sheet.
 13. Apparatus as claimed in claim 1, said apparatus constituting a rotary printing machine in which said drum is a support drum for supporting a flexible sheet-form printing plate. 